Tuesday, February 1, 2011
filed under: Fertility
Micronutrients have long been a source of debate in the sunflower world. University fertilizer specialists normally downplay the usefulness of most micronutrients, based on results of their trials, while others — including some growers — contend micros can provide economic benefits in various situations.
Studies at the USDA-ARS Central Great Plains Research Station at Akron, Colo., in the early 2000s, for example, found that micronutrients applied foliarly two times during the season “did not provide a return on investment that was great enough to pay for the micronutrient application,” reported Akron soil scientist Merle Vigil. Similar results occurred in a Colorado State University study. “In that study, neither soil-applied granules nor foliar applications [of micronutrients] provided any yield advantage, regardless of soil moisture conditions,” Vigil noted.
North Dakota State University soil scientist Dave Franzen says studies done at NDSU in the 1980s looked at micronutrients for both sunflower and corn. The researcher, Joseph Zubriski, “never saw a yield increase in ’flowers, but he did with corn,” Franzen says. “Zinc is one micro we’ve often used with corn because our soils are somewhat low in zinc.”
Franzen says “certain crops are able to extract [nutrients] out of even the low-level soils, and sunflower appears to be one of those crops. In North Dakota, we don’t need to be putting on zinc, iron, manganese or boron. Boron was the one I worked with several years ago, and we really didn’t see a response.”
Tom Johnson is president of TJ Technologies, a Watertown, S.D.-based company that has been developing and marketing micronutrient packages for various crops since the early 1990s. Its TJ Micromix® (available in both liquid and dry formulations) contains calcium, magnesium, boron, copper, iron, manganese and zinc in various percentages. “This product is designed for blending with nitrogen, phosphorus and potassium sources to produce a complete fertilizer to be used as a starter in furrow or in band,” TJ Technologies states.
Johnson’s view on micronutrient use in sunflower is that “a proper combination of nutrients will give a consistent yield response, while the application of individual micronutrients will give a response only when severely deficient.”
He notes that research on sunflower in the latter 1990s at NDSU-Minot and NDSU-Carrington looked at different ratios and combinations of micronutrients to determine whether a difference in ratios would influence final results. “Indeed, it did make a difference,” Johnson says. “As the research progressed, those ratios that did not perform would be eliminated or altered, and the more successful ones stayed in the trials. This was the process used to determine the analysis and formulations of the products we [market] today.”
In Johnson’s opinion, “individual micronutrients [tend to be] applied in quantities that are too high — and the result is a toxicity response that reduces yield.” That’s a broad generalization, he admits, but “in sunflower, boron is important in the development of the reproductive parts of the plant. Too much boron will often produce a response that’s similar to inadequate boron,” he says, adding that TJ Micromix is formulated to keep safe micros that might otherwise cause problems.
Johnson says that micronutrients generally produce the best response when the crop is subject to significant stress (e.g., too hot, too cold, too wet, too dry). Obviously, however, micros are not going to help a plant that’s under extreme stress (e.g., severe drought). “Soil types are not necessarily the deciding factor,” he adds. “But a high pH (7.5 to 8.2) will give a greater yield response than a 6.5 to 7.5. When pH is below 6.0, liming is needed to get proper micronutrient response.” - Don Lilleboe